Photo: Jack Califano There is no equivalent in American history to Zohran Kwame Mamdani becoming, at age 34, the next mayor of New York City . An avowed socialist has never led a city so large, nor has a Muslim — nor, in almost any instance, has someone so young and so unlikely to win as the state assemblyman from Queens. Parallels can be invoked, but none quite fit. In Mamdani’s sudden rise there are echoes of Barack Obama, another man with African roots derided by everyone from Hillary